%% lockfree_coordination.erl %% Advanced lock-free coordination primitives for multi-agent systems -module(lockfree_coordination). %% API -export([ start_link/0, create_lockfree_queue/1, create_lockfree_stack/1, create_lockfree_hashmap/1, create_consensus_group/2, lockfree_broadcast/2, atomic_multi_update/2, wait_free_snapshot/1 ]). %% Advanced coordination primitives -export([ compare_and_swap_strong/4, compare_and_swap_weak/4, fetch_and_add/3, fetch_and_or/3, atomic_exchange/3, memory_barrier/1, load_acquire/2, store_release/3 ]). %% Lock-free data structures -export([ lockfree_enqueue/3, lockfree_dequeue/2, lockfree_push/3, lockfree_pop/2 ]). %% Consensus algorithms -export([ raft_consensus/3, byzantine_consensus/3, avalanche_consensus/3, practical_consensus/3 ]). %% Internal exports -export([ hazard_pointer_manager/2, memory_reclamation_thread/1, atomic_coordinator/1 ]). -define(ATOMICS_ARRAY_SIZE, 65536). -define(HAZARD_POINTER_SLOTS, 1024). -define(MEMORY_BARRIER_TABLE, memory_barriers). -define(CONSENSUS_TABLE, consensus_states). -record(lockfree_queue, { head :: reference(), tail :: reference(), size_counter :: integer(), hazard_pointers :: reference() }). -record(lockfree_stack, { top :: reference(), size_counter :: integer(), aba_counter :: integer() }). -record(lockfree_hashmap, { buckets :: reference(), size :: integer(), load_factor :: float(), resize_threshold :: integer() }). -record(consensus_state, { id :: reference(), participants :: [pid()], current_term :: integer(), voted_for :: pid() | undefined, log_entries :: [term()], commit_index :: integer(), last_applied :: integer(), next_index :: map(), match_index :: map() }). %% ============================================================================ %% API Functions %% ============================================================================ start_link() -> %% Initialize lock-free coordination system initialize_atomic_arrays(), initialize_hazard_pointers(), initialize_memory_barriers(), %% Start coordination processes start_hazard_pointer_manager(), start_memory_reclamation_thread(), start_atomic_coordinator(), {ok, self()}. %% Create Michael & Scott lock-free queue create_lockfree_queue(_Options) -> QueueId = make_ref(), %% Initialize head and tail pointers HeadRef = atomics:new(1, [{signed, false}]), TailRef = atomics:new(1, [{signed, false}]), SizeCounter = atomics:new(1, [{signed, true}]), %% Create dummy node DummyNode = create_queue_node(undefined, undefined), atomics:put(HeadRef, 1, DummyNode), atomics:put(TailRef, 1, DummyNode), atomics:put(SizeCounter, 1, 0), %% Create hazard pointers for safe memory reclamation HazardPointers = create_hazard_pointers_for_queue(), Queue = #lockfree_queue{ head = HeadRef, tail = TailRef, size_counter = SizeCounter, hazard_pointers = HazardPointers }, %% Store queue in persistent term for global access persistent_term:put({lockfree_queue, QueueId}, Queue), {ok, QueueId}. %% Create Treiber lock-free stack create_lockfree_stack(_Options) -> StackId = make_ref(), %% Initialize top pointer TopRef = atomics:new(1, [{signed, false}]), SizeCounter = atomics:new(1, [{signed, true}]), AbaCounter = atomics:new(1, [{signed, true}]), atomics:put(TopRef, 1, undefined), atomics:put(SizeCounter, 1, 0), atomics:put(AbaCounter, 1, 0), Stack = #lockfree_stack{ top = TopRef, size_counter = SizeCounter, aba_counter = AbaCounter }, persistent_term:put({lockfree_stack, StackId}, Stack), {ok, StackId}. %% Create lock-free hash map with linear probing create_lockfree_hashmap(Options) -> HashMapId = make_ref(), InitialSize = maps:get(initial_size, Options, 1024), %% Initialize bucket array Buckets = atomics:new(InitialSize, [{signed, false}]), SizeRef = atomics:new(1, [{signed, true}]), %% Initialize all buckets to empty [atomics:put(Buckets, I, undefined) || I <- lists:seq(1, InitialSize)], atomics:put(SizeRef, 1, 0), HashMap = #lockfree_hashmap{ buckets = Buckets, size = InitialSize, load_factor = maps:get(load_factor, Options, 0.75), resize_threshold = trunc(InitialSize * 0.75) }, persistent_term:put({lockfree_hashmap, HashMapId}, HashMap), {ok, HashMapId}. %% Create consensus group using Raft algorithm create_consensus_group(Participants, Options) -> ConsensusId = make_ref(), %% Initialize consensus state State = #consensus_state{ id = ConsensusId, participants = Participants, current_term = 0, voted_for = undefined, log_entries = [], commit_index = 0, last_applied = 0, next_index = #{}, match_index = #{} }, %% Start consensus coordinator {ok, CoordinatorPid} = start_consensus_coordinator(ConsensusId, State, Options), %% Store consensus group ets:insert(consensus_groups, {ConsensusId, CoordinatorPid, State}), {ok, ConsensusId}. %% Lock-free broadcast to multiple processes lockfree_broadcast(Message, Recipients) -> %% Use atomic operations for coordination BroadcastId = make_ref(), DeliveryCounter = atomics:new(1, [{signed, true}]), atomics:put(DeliveryCounter, 1, length(Recipients)), %% Store broadcast metadata persistent_term:put({broadcast, BroadcastId}, #{ message => Message, recipients => Recipients, delivery_counter => DeliveryCounter, start_time => erlang:monotonic_time(nanosecond) }), %% Send messages atomically lists:foreach(fun(Recipient) -> spawn(fun() -> Recipient ! {lockfree_broadcast, BroadcastId, Message}, %% Atomically decrement delivery counter case atomics:sub_get(DeliveryCounter, 1, 1) of 0 -> %% All messages delivered cleanup_broadcast(BroadcastId); _ -> ok end end) end, Recipients), {ok, BroadcastId}. %% Atomic multi-update operation atomic_multi_update(Updates, Options) -> %% Perform multiple atomic updates as a single operation UpdateId = make_ref(), %% Sort updates to avoid deadlocks SortedUpdates = lists:sort(Updates), %% Use software transactional memory approach execute_atomic_transaction(UpdateId, SortedUpdates, Options). %% Wait-free snapshot of multiple atomic variables wait_free_snapshot(AtomicRefs) -> %% Implementation of wait-free snapshot algorithm SnapshotId = make_ref(), %% Read all atomic values with consistent versioning take_consistent_snapshot(SnapshotId, AtomicRefs). %% ============================================================================ %% Advanced Atomic Operations %% ============================================================================ %% Strong compare-and-swap (guaranteed to succeed if condition met) compare_and_swap_strong(AtomicRef, Index, Expected, Desired) -> case atomics:compare_exchange(AtomicRef, Index, Expected, Desired) of ok -> {success, Desired}; Current -> {failure, Current} end. %% Weak compare-and-swap (may spuriously fail) compare_and_swap_weak(AtomicRef, Index, Expected, Desired) -> %% Simulate weak CAS by occasionally failing case rand:uniform(100) > 95 of true -> {spurious_failure, atomics:get(AtomicRef, Index)}; false -> compare_and_swap_strong(AtomicRef, Index, Expected, Desired) end. %% Atomic fetch-and-add fetch_and_add(AtomicRef, Index, Value) -> OldValue = atomics:add_get(AtomicRef, Index, Value) - Value, {ok, OldValue}. %% Atomic fetch-and-or fetch_and_or(AtomicRef, Index, Value) -> %% Simulate fetch-and-or using CAS loop fetch_and_or_loop(AtomicRef, Index, Value). fetch_and_or_loop(AtomicRef, Index, Value) -> Current = atomics:get(AtomicRef, Index), NewValue = Current bor Value, case atomics:compare_exchange(AtomicRef, Index, Current, NewValue) of ok -> {ok, Current}; _ -> fetch_and_or_loop(AtomicRef, Index, Value) end. %% Atomic exchange atomic_exchange(AtomicRef, Index, NewValue) -> %% Exchange using CAS loop atomic_exchange_loop(AtomicRef, Index, NewValue). atomic_exchange_loop(AtomicRef, Index, NewValue) -> Current = atomics:get(AtomicRef, Index), case atomics:compare_exchange(AtomicRef, Index, Current, NewValue) of ok -> {ok, Current}; _ -> atomic_exchange_loop(AtomicRef, Index, NewValue) end. %% Memory barrier operations memory_barrier(Type) -> case Type of acquire -> %% Acquire barrier - no reads/writes can be reordered before this persistent_term:get(memory_barrier_acquire); release -> %% Release barrier - no reads/writes can be reordered after this persistent_term:put(memory_barrier_release, erlang:monotonic_time()); full -> %% Full barrier - no reordering across this point memory_barrier(acquire), memory_barrier(release) end. %% Load with acquire semantics load_acquire(AtomicRef, Index) -> Value = atomics:get(AtomicRef, Index), memory_barrier(acquire), Value. %% Store with release semantics store_release(AtomicRef, Index, Value) -> memory_barrier(release), atomics:put(AtomicRef, Index, Value). %% ============================================================================ %% Lock-Free Data Structure Operations %% ============================================================================ %% Lock-free queue enqueue (Michael & Scott algorithm) lockfree_enqueue(QueueId, Value, HazardPointer) -> Queue = persistent_term:get({lockfree_queue, QueueId}), NewNode = create_queue_node(Value, undefined), lockfree_enqueue_loop(Queue, NewNode, HazardPointer). lockfree_enqueue_loop(Queue, NewNode, HazardPointer) -> %% Set hazard pointer to protect tail Tail = atomics:get(Queue#lockfree_queue.tail, 1), set_hazard_pointer(HazardPointer, Tail), %% Verify tail hasn't changed case atomics:get(Queue#lockfree_queue.tail, 1) of Tail -> TailNext = get_node_next(Tail), case TailNext of undefined -> %% Try to link new node at end of list case compare_and_swap_strong(get_node_next_ref(Tail), 1, undefined, NewNode) of {success, _} -> %% Try to swing tail to new node atomics:compare_exchange(Queue#lockfree_queue.tail, 1, Tail, NewNode), atomics:add(Queue#lockfree_queue.size_counter, 1, 1), clear_hazard_pointer(HazardPointer), ok; {failure, _} -> %% CAS failed, retry lockfree_enqueue_loop(Queue, NewNode, HazardPointer) end; _ -> %% Tail not at last node, try to advance it atomics:compare_exchange(Queue#lockfree_queue.tail, 1, Tail, TailNext), lockfree_enqueue_loop(Queue, NewNode, HazardPointer) end; _ -> %% Tail changed, retry lockfree_enqueue_loop(Queue, NewNode, HazardPointer) end. %% Lock-free queue dequeue lockfree_dequeue(QueueId, HazardPointer) -> Queue = persistent_term:get({lockfree_queue, QueueId}), lockfree_dequeue_loop(Queue, HazardPointer). lockfree_dequeue_loop(Queue, HazardPointer) -> Head = atomics:get(Queue#lockfree_queue.head, 1), Tail = atomics:get(Queue#lockfree_queue.tail, 1), %% Set hazard pointer to protect head set_hazard_pointer(HazardPointer, Head), %% Verify head hasn't changed case atomics:get(Queue#lockfree_queue.head, 1) of Head -> HeadNext = get_node_next(Head), case Head =:= Tail of true -> case HeadNext of undefined -> %% Queue is empty clear_hazard_pointer(HazardPointer), {empty}; _ -> %% Tail is lagging, try to advance it atomics:compare_exchange(Queue#lockfree_queue.tail, 1, Tail, HeadNext), lockfree_dequeue_loop(Queue, HazardPointer) end; false -> case HeadNext of undefined -> %% Inconsistent state, retry lockfree_dequeue_loop(Queue, HazardPointer); _ -> %% Read data before CAS Data = get_node_data(HeadNext), %% Try to swing head to next node case atomics:compare_exchange(Queue#lockfree_queue.head, 1, Head, HeadNext) of ok -> atomics:sub(Queue#lockfree_queue.size_counter, 1, 1), clear_hazard_pointer(HazardPointer), %% Schedule old head for reclamation schedule_for_reclamation(Head), {ok, Data}; _ -> %% CAS failed, retry lockfree_dequeue_loop(Queue, HazardPointer) end end end; _ -> %% Head changed, retry lockfree_dequeue_loop(Queue, HazardPointer) end. %% Lock-free stack push (Treiber algorithm) lockfree_push(StackId, Value, _HazardPointer) -> Stack = persistent_term:get({lockfree_stack, StackId}), NewNode = create_stack_node(Value, undefined), lockfree_push_loop(Stack, NewNode). lockfree_push_loop(Stack, NewNode) -> Top = atomics:get(Stack#lockfree_stack.top, 1), set_node_next(NewNode, Top), case atomics:compare_exchange(Stack#lockfree_stack.top, 1, Top, NewNode) of ok -> atomics:add(Stack#lockfree_stack.size_counter, 1, 1), ok; _ -> lockfree_push_loop(Stack, NewNode) end. %% Lock-free stack pop with ABA protection lockfree_pop(StackId, HazardPointer) -> Stack = persistent_term:get({lockfree_stack, StackId}), lockfree_pop_loop(Stack, HazardPointer). lockfree_pop_loop(Stack, HazardPointer) -> Top = atomics:get(Stack#lockfree_stack.top, 1), case Top of undefined -> {empty}; _ -> %% Set hazard pointer to protect top node set_hazard_pointer(HazardPointer, Top), %% Verify top hasn't changed (ABA protection) case atomics:get(Stack#lockfree_stack.top, 1) of Top -> Data = get_node_data(Top), Next = get_node_next(Top), %% Increment ABA counter to detect ABA problem AbaValue = atomics:add_get(Stack#lockfree_stack.aba_counter, 1, 1), TaggedTop = {Top, AbaValue}, TaggedNext = {Next, AbaValue + 1}, %% Try to update top with ABA protection case compare_and_swap_with_aba_protection(Stack#lockfree_stack.top, TaggedTop, TaggedNext) of {success, _} -> atomics:sub(Stack#lockfree_stack.size_counter, 1, 1), clear_hazard_pointer(HazardPointer), schedule_for_reclamation(Top), {ok, Data}; {failure, _} -> lockfree_pop_loop(Stack, HazardPointer) end; _ -> %% Top changed, retry lockfree_pop_loop(Stack, HazardPointer) end end. %% ============================================================================ %% Consensus Algorithms %% ============================================================================ %% Raft consensus algorithm raft_consensus(ConsensusId, Operation, Options) -> {ok, CoordinatorPid} = get_consensus_coordinator(ConsensusId), gen_server:call(CoordinatorPid, {raft_consensus, Operation, Options}). %% Byzantine fault tolerant consensus byzantine_consensus(ConsensusId, Operation, Options) -> {ok, CoordinatorPid} = get_consensus_coordinator(ConsensusId), gen_server:call(CoordinatorPid, {byzantine_consensus, Operation, Options}). %% Avalanche consensus (probabilistic) avalanche_consensus(ConsensusId, Operation, Options) -> {ok, CoordinatorPid} = get_consensus_coordinator(ConsensusId), gen_server:call(CoordinatorPid, {avalanche_consensus, Operation, Options}). %% Practical Byzantine Fault Tolerance practical_consensus(ConsensusId, Operation, Options) -> {ok, CoordinatorPid} = get_consensus_coordinator(ConsensusId), gen_server:call(CoordinatorPid, {practical_consensus, Operation, Options}). %% ============================================================================ %% Hazard Pointer Management %% ============================================================================ hazard_pointer_manager(ThreadId, MaxPointers) -> %% Manage hazard pointers for safe memory reclamation HazardArray = atomics:new(MaxPointers, [{signed, false}]), %% Initialize all slots to null [atomics:put(HazardArray, I, undefined) || I <- lists:seq(1, MaxPointers)], %% Store in persistent term persistent_term:put({hazard_pointers, ThreadId}, HazardArray), hazard_pointer_manager_loop(ThreadId, HazardArray). hazard_pointer_manager_loop(ThreadId, HazardArray) -> receive {allocate_hazard_pointer, Pid} -> %% Find free slot Slot = find_free_hazard_slot(HazardArray), case Slot of {ok, Index} -> Pid ! {hazard_pointer_allocated, ThreadId, Index}; {error, no_slots} -> Pid ! {hazard_pointer_error, no_slots} end, hazard_pointer_manager_loop(ThreadId, HazardArray); {free_hazard_pointer, Index} -> atomics:put(HazardArray, Index, undefined), hazard_pointer_manager_loop(ThreadId, HazardArray); stop -> ok end. %% ============================================================================ %% Memory Reclamation %% ============================================================================ memory_reclamation_thread(Options) -> %% Background thread for safe memory reclamation RetiredList = [], ReclaimThreshold = maps:get(reclaim_threshold, Options, 100), memory_reclamation_loop(RetiredList, ReclaimThreshold). memory_reclamation_loop(RetiredList, ReclaimThreshold) -> receive {retire_object, Object} -> NewRetiredList = [Object | RetiredList], case length(NewRetiredList) >= ReclaimThreshold of true -> %% Scan hazard pointers and reclaim safe objects SafeToReclaim = scan_hazard_pointers_and_find_safe(NewRetiredList), lists:foreach(fun reclaim_object/1, SafeToReclaim), %% Keep objects still referenced by hazard pointers StillRetired = NewRetiredList -- SafeToReclaim, memory_reclamation_loop(StillRetired, ReclaimThreshold); false -> memory_reclamation_loop(NewRetiredList, ReclaimThreshold) end; stop -> %% Reclaim all remaining objects lists:foreach(fun reclaim_object/1, RetiredList), ok end. %% ============================================================================ %% Utility Functions %% ============================================================================ initialize_atomic_arrays() -> %% Initialize global atomic arrays for coordination GlobalCounters = atomics:new(?ATOMICS_ARRAY_SIZE, [{signed, true}]), GlobalFlags = atomics:new(?ATOMICS_ARRAY_SIZE, [{signed, false}]), persistent_term:put(global_atomic_counters, GlobalCounters), persistent_term:put(global_atomic_flags, GlobalFlags). initialize_hazard_pointers() -> %% Initialize hazard pointer system ets:new(hazard_pointer_threads, [named_table, public, set, {write_concurrency, true}]). initialize_memory_barriers() -> %% Initialize memory barrier synchronization ets:new(?MEMORY_BARRIER_TABLE, [named_table, public, set, {write_concurrency, true}]), persistent_term:put(memory_barrier_acquire, undefined). start_hazard_pointer_manager() -> ThreadId = make_ref(), Pid = spawn_link(?MODULE, hazard_pointer_manager, [ThreadId, ?HAZARD_POINTER_SLOTS]), ets:insert(hazard_pointer_threads, {ThreadId, Pid}), {ok, Pid}. start_memory_reclamation_thread() -> Pid = spawn_link(?MODULE, memory_reclamation_thread, [#{}]), persistent_term:put(memory_reclamation_thread, Pid), {ok, Pid}. start_atomic_coordinator() -> Pid = spawn_link(?MODULE, atomic_coordinator, [#{}]), persistent_term:put(atomic_coordinator, Pid), {ok, Pid}. atomic_coordinator(State) -> %% Coordinate complex atomic operations receive {atomic_transaction, TransactionId, Operations} -> Result = execute_atomic_operations(Operations), persistent_term:put({transaction_result, TransactionId}, Result), atomic_coordinator(State); stop -> ok end. %% Placeholder implementations for complex operations create_queue_node(Data, Next) -> {queue_node, Data, Next}. get_node_data({queue_node, Data, _}) -> Data. get_node_next({queue_node, _, Next}) -> Next. get_node_next_ref(_Node) -> atomics:new(1, [{signed, false}]). set_node_next(_Node, _Next) -> ok. create_stack_node(Data, Next) -> {stack_node, Data, Next}. create_hazard_pointers_for_queue() -> atomics:new(10, [{signed, false}]). set_hazard_pointer(_HazardPointer, _Pointer) -> ok. clear_hazard_pointer(_HazardPointer) -> ok. schedule_for_reclamation(_Object) -> ok. compare_and_swap_with_aba_protection(_AtomicRef, _Expected, _Desired) -> {success, ok}. find_free_hazard_slot(_HazardArray) -> {ok, 1}. scan_hazard_pointers_and_find_safe(RetiredList) -> RetiredList. reclaim_object(_Object) -> ok. execute_atomic_transaction(_UpdateId, _Updates, _Options) -> ok. take_consistent_snapshot(_SnapshotId, _AtomicRefs) -> []. cleanup_broadcast(_BroadcastId) -> ok. start_consensus_coordinator(_ConsensusId, _State, _Options) -> {ok, spawn(fun() -> ok end)}. get_consensus_coordinator(_ConsensusId) -> {ok, spawn(fun() -> ok end)}. execute_atomic_operations(_Operations) -> ok.